Gate Drive Transformer Circuit

The gate drive described in this paper uses a printed circuit board based transformer in combination with the memory effect of the power mosfet input capacitance to achieve the isolation.

Gate drive transformer circuit. Gate drive transformer circuit maintains fast turn off time this gate drive transformer gdt circuit allows the drive signal to the mosfet to range from 50 down to 0 while still offering a fast. These devices provide electrical pulses for turning on and off semiconductors such as high voltage power mosfets or igbts. A special section deals with the gate drive requirements of the mosfets in synchronous rectifier applications. A gate drive circuit with very low impedance insures that the gate voltage is not exceeded in normal operation.

A gate drive transformer is needed in a smps to control the timing of the circuit. Zeners are frequently used to protect the gate from transients. Gate drive transformers are essentially pulse transformers that are used. Some gate drive transformers simply deliver a voltage pulse or a series of voltage pulses to a semiconductor gate.

For more information see the overview for mosfet and igbt gate drivers product page. This is explained in more detail in the next section. A gate drive transformer isolates the controlling gate drive circuit from the switch node when driving the mosfet gate and may also scale the output voltage via an appropriate primary to secondary turns ratio. This transformer is a bi directional link between the ground referenced control ic and the floating gate drive.

In some applications digital isolators or opto couplers may provide the means to drive mosfet s directly but gate drive transformers are preferred for higher voltage requirements and have the advantage of much lower turn on and turn off delay times as well as the capability to. They also are used for voltage isolation and impedance matching. In addition to the transformer it also consists of the associated reset components such as the blocking capacitor c primary resistor r gate resistor r g back to back zener diodes etc. They also are used for voltage isolation and impedance matching.

These devices provide electri cal pulses for turning on and off semiconductors such as high voltage power mosfets or igbts. Coilcraft s off the shelf gate drive transformers simplify the design of your gate drive circuit and shorten design cycle time. The basic circuit of a transformer based isolated gate drive is relatively large. A gate drive transformer isolates the controlling gate drive circuit from the switch node when driving the mosfet gate and may also scale the output voltage via an appropriate primary to secondary turns ratio.

Gate driver circuits need an isolated floating bias supply to maintain the required turn on bias when the fet source rises to the input voltage. Procedure for ground referenced and high side gate drive circuits ac coupled and transformer isolated solutions are described in great details. Most circuit designers would consider these gate drive transformers to be a type of pulse transformer.